Proportioning control apparatus and method of controlling the operation thereof



March 23, 1937.

MQZZQLWWW (Wm/wag Patented Ma 23; 1937 rnoron'rromo coivrnor. arrmrosAND rnrrnon or conrnoumc. rm: OPERATION rnnasor Guido Wiinsch,Berlin-Steglits, Germany, alsignor to Askania-Werke A. G. vormalsCenital Werkstatt Dessau and Carl Bomber:-

Friedenau, a corporation of Germany Application October 30, 1984,ScrialNo. 150,700 In Germany November 30, 1933 4 Claims. (c1. 131-164)-This invention relates to proportioning control apparatus of the generaltype shown in U. 8. Patent No. 1,558,529, dated October 27, 1925 and,among other objects, aims to provide an im- 5 proved method and meansfor controlling themixture of two media, such as gases, liquids or otherfluent materials by balancing two impulses representing the respectiveflows created by differential pressures within the two media, usingvariable restrictions the free areas oi which are increased or decreasedsimultaneously. The invention will he explained in connection with a gasproportioning device or regulator such as is conly used for controllingthe ure of air and gas or separate gases supplied to a furnace. However,the invention is not to he considered as being restricted in any senseto this specific application or to the particular em w thereoi shown inthe accompanying drawin other aims and advantages of the invention willappear in the specification, when considered in connection with theaccompanying drawing.

' "wherein:

Ihe figure is an elevation, partly in section, showing the preferredform of apparatus for practicing'the method.

The aforesaid patentrelates to a regulator or ratio control mechanismwherein the mikture of two gases is governed by diflerential pressurescreated on opposite sides of fixed orifice plates arranged in the gasconduits.- The mechanism utilizes a well known jet pipe system to eifect the regulation by balancing the diflerential pressures against eachother. Such a system is satisfactory only when the how ranges of thegases are comparatively small.

as the diiierential pressure increases or decreases,

the sensitivity of the control mechanism is decreased. To make such asystem operate. catty factorily for wide variations in flow, it isimportent that the variations in the dlflercntial pressures shall berelatively small. In other words, the free areas of the orifices shouldbe changed as the flow increasesor decreases so as to modify thepressure differential only slightly and keep within the range of theproportional control mechanism. Incidentally, there is a maximum and aminimum pressure at which a diaphragm control mechanism will operatesatisfactorily and 56. this applies to more or less sensitive mechanismsIt will not operate satisfactorily when there are wide variationsindifof other types. This invention therefore aims to provide such asystem or mechanism which operates satisfactorily to control theratiocoi gases or other media for a relatively wide degree of changes inflow.

Referring particularly to the drawing, it will be assumed that thesystem shown is applied to the regulation of two gases. The primary gasflows through a conduit l and the secondary gas I through a conduit 2.These gases mix and are delivered to a common conduit 3 or to a chamber,as the case may be. Instead of employing fixed orifice plates in theconduits, butterfly valves 4 and 5 are used to vary the free areas ofthe respective conduits in response to changes orvariations in flow.Each of these butterfly valves is shown as having a crank arm 6connected by a pivoted linl: l to a pistonrod t carrying a piston t in acylinder it, the arrangement being such that the butterfly valves movesimultaneously. To utilize a diflerentiol pressure on opposite sides oithe butterfly valve t in the conduit i, pipes ii and it are connected tosaid conduit on opposite sides of the valve and lead to a, diaphragmcasing it on opposite sides of a diaphragm it which carries a push-piperstem it extending through an opening in one side I. oi a regulatorcasingit; Likewise; pipes 'or' conduits it and it are connected to thesecondary was conduit 2 and lead to a diaphragm casing .it on oppositesides of a diaphragm is whi h carries a push-pin or ii extending throughthe opposite side or wail-o1 the regulator casin it, the arrangt beingsuch that the two push-pins or stems it and 21! act in opposition toeach other. The push-pin it carried by the phragm'it is'shown as actingdirectly on a pivoted jet noz-. zle 22; while the push-pin 1| acts on apivoted counter-lever 28. Between the counter-lever 23 and the nozzle 22there is arranged a ratioadlusting disk' 2 carried on a ratio slider 25which projects through the mono: casing. The arrangement is suchthat-the ratio can be varied by moving the ratio slider in or out.However, this particular mechanism forms no part of the presentinvention. The jet nozzle 22 is shown as being counterbalanced by anadjustable weight it screwed on a stem proiecting-beyondits pivot. Also,the counter-lever I8 is preferably counterweighted by a similaradjustable weight 21. The adjustable slider 25 does not interfere withthe swinging movement oi the nozzle.

It will be seen that the differential pressures on the diaphragms actagainst each other and against the jet pipe. when the differentialpressures balance each other, the Jet pipe is in the neutral positionshown. It is adapted to be moved either to the right or to the left whenthe presssures are unbalanced. The jet pipe cooperates tial pressure isincreased in the primary. gas conduit, the Jet pipe will be moved to theleft and 15 thereby discharge into the left hand end of the cylinder tomove the piston I to the right. This will open both butterflies furtheruntil equilibrium is again established or the pressures balance eachother. The jet pipe is preferably supplied 20 with oil or other liquidby a pump 32 which is operated by a motor I3. The pump is connected tothe jet pipe by a pipe 84 and the liquid is circulated through the pumpby means of a return pipe 35 connected to the bottom portion of 25 theregulator casing. 4

The quantity of gases flowing through the respective conduits may bemeasured by suitable flow meters It and 3'! connected to thediflerential pressure pipes. Moreover, the quantity of 3 primary gas maybe varied by a suitable valve II in the conduit I.

From the foregoing description, it will be seen that the free areas ofthe openings or restrictions formed by .the butterflies are varied when3 their positions are changed and it is easy to calculate their areas soas to obtain differential pressures for diiferent flows within the rangeof I the instrument. The butterflies are mechanically connected becauseit is desirable in both cases to 40 have a decrease in differentialpressures for an increase in flow and an increase in differentialpressure for a decrease in flow. The most important point to beconsidered in this calculation is the dimension of the butterfly valve4.

45 It is such that in spite of its movement, the flow of gas is onlyslightly affected. This is done by making the diameter of the primarygas line rela-' tively large as shown and by limiting the stroke of thevalve 4. Such a combination serves to to create a relatively smalldifferential pressure, while the butterfly in the gas line 2 regulatesthe flow of secondary gas. The movement of the butterfly valve 8 in theline 2 effects materially the flow of secondary 888 since the conduit 2is 66 smaller. Thus, the regulation of the mixture or ratio iscontrolled accurately because the press sure differentials in theprimary gas conduit are kept well within the range of the instrument.The amount oi the secondary gas is determined by the opening of thevalve 38 and.at the same time, the impulse obtained from the'movement orflow of the primary gas is affected by the controllingvalveinsuehamannerthatforsnincreasein duits, movable restricting meansin each of the conduits; means connecting said mtricting means tooperate simultaneously; and a regulator operable by difl'erentialpressures in either of the conduits connected to control the movementsof said restricting means.

2. In ratio control apparatus for separate fluid mediatobemixed,apairofconduitsfcrthe media; mechanically connected andsimultaneously movable restricting devices in the conduits; actuatingmeans associated with the mechanical connections to impart controllingmovements to said restricting devices; and a regulator operable bydifferential pressures in either of the conduits connected to govern theoperation of said actuating means.

3. In ratio control apparatus for separate fluid media to be mixed,a'pair of conduits for the media; mechanically connected andsimultaneously movable butterfly valves in the conduits; a regulatoroperated by the pressure differences at said valves and means governedby said regulator to actuate said valves.

4'. That method of proportioning the flow of primary and secondary fluidmedia passing through conduits, which is charaeterimdby restricting theflow in the conduits to create differential pressures; using thediflerential pressures created in either of the conduits tooperate a.regulator; and simultaneously varying the restrictions by the governingaction'of the regulator whereby to reduce the range of differoumo women.

